Helical pile foundation system

ABSTRACT

A post foundation system is provided. The system has a shaft with a helical disk attached to one end and a post support attached to the other end. The helical disk drives the shaft into the ground as a rotational force is applied to the shaft. A fin section is rotatably coupled about the shaft between its first and second ends. The fin section can have one or more fins extending outwardly from the shaft. The fin section engages the ground to stabilize the post foundation system as the shaft of the post foundation system is driven into the ground.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/122,840 filed Sep. 5, 2018, now U.S. Pat. No. 10,526,758 issued Jan.7, 2020, which is incorporated by reference.

TECHNICAL FIELD

The invention generally relates to sign foundations and, morespecifically, to a helical pile used as a foundation base for a roadwaysign.

BACKGROUND

Typically, roadway signs comprise a sign and a post to which the sign isattached. In some cases, roadway signs are installed by simply drivingthe post into the ground at the desired location. In other cases,roadway sign posts are implanted in a concrete encasement which isburied in the ground.

SUMMARY

Various embodiments of the invention are directed to an improvedfoundation system for roadway signage and other posts. Typical sign postfoundations suffer from a number of drawbacks. When sign posts aresimply driven into the ground, there is very little lateral support andany support is determined by the integrity of the earth into which thepost is driven. Weak or moving soil, or soil erosion, can quickly causea sign to lean or fall. Signs that utilize concrete foundations likewisehave drawbacks. The concrete foundations themselves often fail overtime. Heating and cooling can cause gaps between the sign post and theconcrete encasement. Moreover, the process of installing a sign with aconcrete foundation is time consuming in that the sign must be installedin at least two discrete steps. First, the concrete must be poured andthen properly cured. Then, after a period of time, the sign post isinstalled. This presents particular problems in remote areas as traveltime between the installation site and manufacturing facility isdoubled. All of the above drawbacks can lead to increased cost incurredin a roadway sign installation project.

Certain embodiments of the present invention utilize a helical pile asthe foundation base for roadway signage. In certain cases, thisincreases the lateral strength of the sign (or sign post) to allow formeeting code requirements in multiple soil types. Certain aspects of theinvention further address the lack of lateral resistance usuallyassociated with the slender shaft of a helical pile in a foundationapplication. Various embodiments of the invention also reduce the numberof installation steps and the time needed to complete installation.

In one example embodiment the invention is a post foundation system,which includes a shaft having a first and a second end. A helical diskis affixed to or located at the first end of the shaft and a postsupport is affixed to or located at the second end of the shaft. Thesystem further includes a fin section rotatably coupled about the shaftbetween the first and second ends of the shaft. The fin section may beadapted to engage the ground as the post foundation system is driveninto the ground in order to help provide stability to the postfoundation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a foundation system in accordance with anexample embodiment; and

FIG. 2 is a plan view of a base plate and fins of the foundation systemof FIG. 1.

DETAILED DESCRIPTION

In certain embodiments a foundation base system is provided for mountingdifferent types of sign posts and for other applications. In an exampleembodiment as shown in FIG. 1, a foundation system 10 includes a shaft12. The shaft can be of any suitable dimensions, such as length, innerand outer diameter, wall thickness, etc. In this example, the shaft isshown as being cylindrical with a circular cross-section. In certainapplications, a circular, cylindrical shaft may be preferable. Forexample, a circular, cylindrical shaft may provide a lower amount ofresistance when the foundation is driven into soil than a cylindricalshaft having a square cross-section for example. However, the inventionalso encompasses shafts that are partly solid and with differingcross-sectional shapes.

In certain applications, such as when the foundation base system is usedfor installing common roadway signs (e.g., a stop sign or a speed limitsign), the dimensions of the shaft can become important. In such cases,it is preferable that the shaft is from about 30 to about 60 incheslong, circular in cross-section, with an outside diameter of from about2.5 to about 10 inches and an inside diameter of from about 2 to about 9inches. Even more preferably, the length is about 39 inches, the outsidediameter is about 4 inches and the inside diameter is about 3.5 inches.The reason for these preferred dimensions is so that the foundation basewill accommodate sign posts having conventional, or standard,dimensions. Another reason is so that the foundation base providesacceptable support (e.g., resistance to lateral force within a certainrange) and so that cost of the foundation base is minimized. The shaft(as well as the other components of the foundation base system) may bemade from steel. However, it is within the scope of the invention toutilize different materials from some or all of the components.

A soil plug 18 is welded, or otherwise attached, to the inside lowerpart of a main shaft at or near the distal end of shaft 12 that will bedriven into the ground. Soil plug 18 prevents excessive soil fromcollecting within the shaft as foundation system 10 is advanced into thesoil. A helical disk 14 is welded, or otherwise mounted, to the outsideof shaft 12. Preferably, helical disk 14 is attached to shaft 12 at, ornear a distal end thereof, which is the end that will be driven into theground. A starter tip 16 is welding to a bottom side of soil plug 18.Preferably, starter tip 16 comprises a “twist tip” to open the earth forshaft 12 to be pulled into the ground via the downward pull of helicaldisk 14. Shaft 12 may be advanced with the use of a hydraulic torquemotor.

A fin section 22 is mounted about shaft 12. Preferably, fin section 22is positioned so that its bottom edge is approximately from about 12inches to about 18 inches above the ground end of shaft 12. This is sothe fin section is buried an acceptable distance into the ground whenfoundation system 10 is at its preferred depth. It should be noted thatthe length of shaft 12, the positioning of fin section 22 and the shapeand dimensions of the fin section and other components may be modifiedwithin the scope of the invention to accommodate a number of factorssuch as sign type, sign size, post type and size, soil conditions, sheerforce requirements, etc.

In one example embodiment, fin section 22 comprises a sleeve 30 to whichone or more fins 20 are attached. Preferably, sleeve 30 has the samecross-sectional shape as shaft 12 with an inside diameter slightlylarger than the outside diameter of shaft 12. In one example embodiment,a plurality of fins 20 is attached. In the example shown in FIGS. 1 and2, three fins 20 are attached to sleeve 30 and are spaced equidistantabout the exterior surface of sleeve 30. It should be noted that fins 20may be made from any suitable material including, for example, steelplate. It should also be noted that the number of fins may be greaterthan, or less than, the three fins illustrated in the exampleembodiment.

In the illustrated example, fins 20 have a leading edge 41, a trailingedge 42, an outer edge 43, and an inner edge 44. Inner edge 44 is theedge that is mounted to sleeve 30. Leading edge 41 is angled from apoint where it meets inner edge 44 to a point where it meets outer edge43. Trailing edge is even, or level, from inner edge 44 to outer edge43. In this regard, outer edge 43 is shorter than inner edge 44. Incertain cases, this general shape of fins 20 is preferable in order tocreate a wedge effect as fin section 22 is advanced into the ground andto save material in the formation of the fins. Preferably, inner edge 44is from about 12 inches to about 24 inches in length. Preferably, outeredge 43 is from about 8 inches to about 20 inches in length. Preferably,trailing edge 42 (or the lateral distance between inner and outer edges44 and 43) is from about 4 inches to about 12 inches in length.Preferably, the angle of leading edge 41 is from about 30 degrees toabout 45 degrees. Among other things, these dimensions create fins thathave an appropriate surface area to provide sufficient lateral supportfor common roadway signs. Of course, as stated elsewhere herein, itshould be noted that the fin shape and dimensions may be modified toaccount for different factors.

A first sleeve retainer ring 24 is welded, or otherwise attached, toshaft 12 to hold the lower part of the fin section in place on shaft 12.Fin section 22 may be mounted onto shaft 12 such that the leading (orbottom) end of sleeve 30 abuts first sleeve retainer ring 24. A secondsleeve retainer ring 26 is provided at the opposite end of sleeve 30(i.e., above sleeve 30) to hold fin section 22 in place along the lengthof shaft 12.

Fin section 22 rotates freely about shaft 12. Therefore, as foundationsystem 10 is advanced into the ground, and as the leading edges of fins20 come in contact with the soil, fin section 22 does not rotate asshaft 12 continues to rotate.

In the example embodiment two opposing bolt holes 46 are drilled throughshaft 12. Common sign posts have perforations at least in the regionnear the ground end. Bolt holes 46 are aligned such that when a signpost is inserted into shaft 12 of foundation system 10, a bolt may beinserted through bolt holes 46 and likewise through a set of opposingperforations on the sign post. In this manner, up and down movement ofthe sign post, once mounted in foundation system 10, is restricted.Additional pairs of bolt holes may also be incorporated.

A slip joint base 28 is welded, or otherwise attached, to the top distalend of shaft 12. Slip joint base 28 is illustrated in greater detail inFIG. 2. Base 28 preferably has a square, centered opening 50 to acceptan end of a typical sign post. Thus, base 28 accepts both perforatedsign posts and slip-base posts.

Perforated sign post support systems are generally designed to meetNCHRP 350 breakaway standards. In addition, the square post is easilyinstalled. Perforated posts range in size from 1½ to 2½ inches indiameter or width. Various embodiments of the present invention canaccept all of these and support them as a base. Slip-base or breakawaysystems are designed to be mounted to the foundation base system and,upon impact, the breakaway system will release the post and sign fromthe base. The breakaway system is designed to use the perforated signpost as well as round tubing for sign structures. Various embodiments ofthe present invention can accommodate these types of systems.

It should be noted that opening 50 may have other shapes to accommodatedifferently shaped posts and/or other applications. Base 28 is shownwith a generally triangular shape to match the break-away systemscommonly used by most departments of transportation. It should be noted,however, that the base may have other shapes to accommodate differenttypes of break-away systems, different types of posts (e.g., largerposts), and/or different applications. Base 28 has notches 52 at eachcorner. Notches 52 allow access for bolts which typically extend from anupper side of a matching plate on a slip-type post to the lower side ofbase 28 (not shown). This bolt system holds the base of the post (notshown) to the top of foundation system 10.

It should be noted that different modifications can be incorporated intothe various embodiments to accommodate a wide array of signage options.Preferably, the length of the foundation system is set to stay aboveburied lines along roadways but can be lengthened for larger loads. The“slip base” (i.e., base 28 in FIG. 2) can be exchanged to fit a varietyof sign posts. The helical disk 14 can be scaled to meet different soiland load requirements. Other modifications will be apparent to thosehaving ordinary skill in the art.

As should be apparent to one of ordinary skill in the art, many moreaspects and alternatives are well within the scope of the invention,which is defined by the following claims.

What is claimed is:
 1. A post foundation system, comprising: a shaft having a first and a second end; a helical disk affixed to the first end of the shaft; a first retainer ring affixed to the shaft; a sign post slip joint base having a centered opening for receiving a sign post passing therethrough, said sign post slip joint base affixed to the second end of the shaft; a rotatable sleeve carried by the shaft between the first retainer ring and the second end of the shaft, the first retainer ring retains the rotatable sleeve at a predetermined longitudinal position from the second end of the shaft, and, at least one fin carried by the sleeve.
 2. The post foundation system of claim 1, wherein the shaft is tubular, and further comprising: a plug secured within the tubular shaft, the plug positioned adjacent to the first end of the shaft.
 3. The post foundation system of claim 1, wherein the first retainer ring affixed to the shaft is closer to the second end of the shaft than it is to the first end of the shaft.
 4. The post foundation system of claim 1, wherein the rotatable sleeve has a first end and a second end, the first end being closer to the first end of the shaft and wherein the first retainer ring affixed to the shaft maintains the first end of the rotatable sleeve between about 12 inches and about 18 inches from the first end of the shaft.
 5. The post foundation system of claim 1, wherein the shaft will rotate within the rotatable sleeve when the sleeve is held stationary.
 6. The post foundation system of claim 1, wherein the slip joint base having a centered opening has a generally triangular planar shape.
 7. The post foundation system of claim 6, wherein at least one tip of the triangular shaped plate is notched to provide access to a connection device for connecting the slip joint base having a centered opening to the shaft.
 8. The post foundation system of claim 1, wherein the sleeve carries a plurality of fins.
 9. The post foundation system of claim 1, wherein the at least one fin has a leading edge facing the first end of the post foundation system, the leading edge angled toward the second end of the post foundation system as the leading edge extends away from the fin section shaft.
 10. The post foundation system of claim 1, wherein the at least one fin has a leading edge facing the first end of the post foundation system, the leading edge angled away from the second end of the post foundation system as the leading edge extends away from the fin section shaft.
 11. A post foundation system, comprising: a tubular shaft having a first and a second end; a plug secured within the tubular shaft, the plug positioned adjacent to the first end of the shaft; a helical disk affixed to the first end of the shaft; a first retainer ring affixed to the shaft; a sign post slip joint base having a centered opening for receiving a sign post passing therethrough, said sign post slip joint base affixed to the second end of the shaft; a rotatable sleeve carried by the shaft between the first retainer ring and the second end of the shaft, the first retainer ring retains the rotatable sleeve at a predetermined longitudinal position from the second end of the shaft, and, at least one fin carried by the sleeve.
 12. The post foundation system of claim 11, wherein the first retainer ring affixed to the shaft is closer to the second end of the shaft than it is to the first end of the shaft.
 13. The post foundation system of claim 11, wherein the rotatable sleeve has a first end and a second end, the first end being closer to the first end of the shaft and wherein the first retainer ring affixed to the shaft maintains the first end of the rotatable sleeve between about 12 inches and about 18 inches from the first end of the shaft.
 14. The post foundation system of claim 11, wherein the shaft will rotate within the rotatable sleeve when the sleeve is held stationary.
 15. A post foundation system, comprising: a tubular shaft having a first and a second end; a helical disk affixed to the first end of the shaft; a first retainer ring affixed to the shaft, the first retainer ring affixed to the shaft is closer to the second end of the shaft than it is to the first end of the shaft; a sign post slip joint base having a centered opening for receiving a sign post passing therethrough, said sign post slip joint base affixed to the second end of the shaft; a rotatable sleeve carried by the shaft between the first retainer ring and the second end of the shaft, the first retainer ring retains the rotatable sleeve at a predetermined longitudinal position from the second end of the shaft, wherein the tubular shaft will rotate within the rotatable sleeve when the sleeve is held stationary, and, at least one fin carried by the sleeve.
 16. The post foundation system of claim 15, further comprising: a plug secured within the tubular shaft, the plug positioned adjacent to the first end of the shaft.
 17. The post foundation system of claim 15, wherein the rotatable sleeve has a first end and a second end, the first end being closer to the first end of the shaft and wherein the first retainer ring affixed to the shaft maintains the first end of the rotatable sleeve between about 12 inches and about 18 inches from the first end of the shaft. 